The problem with a pack that size is shipping. It exceeds the maximum shipping size as far as m.a. go.
This is from the smc thread.
I called the main USPS number and was directed to a local "Shipping regulations" contact who pointed out that Exhibit 10.20.8 (a table, for us common folk) in section 601 of the "Domestic Mailing Manual" (a.k.a. "DMM", so you quote "DMM 601.10.20.8") states that secondary (meaning "rechargable") Lithium batteries MAY be shipped both via ground and air.
Do a search on the USPS site, print out that page, and take it with you to the post office when you have LiPo batteries to ship.
There are some restrictions:
1) No more than 3 batteries per package
2) No single cell inside a battery to exceed 20 Wh (Watt-hours)
3) No single battery to exceed 100 Wh
That last rule is why Danny said SMC will not be making 7000 mAHr 4S packs - they would exceed 100 Wh and would not be mailable.